This application is for a Continuation (Renewal) of our RO1-44-PRJ68DN1 (4D DSA and 4D Fluoroscopy: Validation of Diagnostic and Therapeutic Capabilities). The proposed research is focused on developing and testing new methods that add further utility to 4D DSA and 4D fluoroscopy. To accomplish these innovations we have defined 3 tasks: 1)test and implement ways in which the temporal information contained in a 4D DSA can be validated and utilized to quantify blood flow, 2)optimize and test methods that would allow a reduction in the x-ray exposure required for a 4D DSA acquisition and, 3)test, optimize and implement on a commercial angiographic system a 4D fluoroscopy application which will allow accurate, real time reconstruction of devices, embed them in a 3D volume and then create virtual fluoroscopic views at any desired viewing angle with no need for gantry movement. Complementing the virtual fluoroscopic views will be endoscopic views showing the intraluminal position of the device in question. To accomplish these tasks three Specific Aims are proposed. Specific Aim 1: further improvement, validation and optimization of the 4D DSA reconstruction algorithm to improve quantitation. Specific Aim 2: development, testing, testing and validation of the use of a very low dose mask for a 4D DSA acquisition. Specific Aim 3: further development of the 4D Fluoroscopy technique. As detailed in the Research Strategy section of the application each of these Specific Aims will include phantom, animal and human subject studies.